Hi,
It is very easy to determine if the "Other converter" is still putting out power. Plug in the RV and unplug your charger. Then turn on a bunch of lights and monitor the battery voltage. Even if it is just a "1/3 - 2/3 - full" led light up on the water panel, you can monitor the battery. If it stays "Full" after a hour of use, or goes from 2/3 to full, then the battery converter is still working. If it drops (and it might take a while to drop the voltage on a large 4D battery) then your converter is not connected.
When I disconnected the converter in one RV, all I did was disconnect one black wire from the converter 120 volt input where it connected to the 20 amp circuit breaker, and install a orange wire nut on that wire. Hopefully some new owner will be able to figure it out - if the electronic charger that I installed ever stops working.
Yes I agree that if you just started the generator, and the charger is putting out a lot of amperage, then the charger can be using more than 500 watts and thus the microwave will overload the generator. The solution is start the generator about 15 - 20 minutes before using the coffee maker or microwave, then the "Peak" charge will be somewhat over by the time you need the microwave. or unplug. Your pick.
Fred.